pH too low?

[Maillis]

It's been a while since I've tested my water in my 55 gallon tank which is very overstocked by most standards (see signature; the school of danios is about 30 fish, bala sharks and pleco are about 6 inches each). The tank is planted with some lower light plants, a few crypts, a couple anubias, and a few java ferns. Everything is growing fine except I've got some beard algea which is growing on everything, especially the slow growing anubias.

All my water parameters check out perfect though, 0 ammonia, 0 nitrite, 10-20 nitrates. Only thing that I'm a little worried about is the pH which is 6.4 according to my liquid test. All the fish are doing fine and I haven't ever had any disease or mystery deaths in the tank. Should I be concerned with such a low pH? It's a lot different than the pH of my tap water which straight from the tap registers over 8.

[savga]

Check your tap water after leaving it out overnight. You will probably find that the pH drops. Mine goes from 8 to about 6.6 .

[TankGirl]

That is a great idea - you may find that if the water has a lot of CO2 in it, it will outgas overnight and the pH drops. Check your KH too, as this goes hand in hand with pH.

If your tap pH is still measuring high, then my next question is how old is the tank? Over time acidification will naturally occur, dropping the pH. As long as you don't do any drastic water changes all at once it should not be a problem, as long as it is stable. If you have a KH of at least 3-4 degrees then it should keep your pH steady. However, it would take years for the pH to drop that many points from acidification.

[Maillis]

Didn't feel like waiting overnight so took a cup of tap water and used an air pump to get the CO2 to outgas. ph is about 7.0, so that's good. I don't have a KH test but I do have a GH test and it shows the tank water as being about 9 degrees. Anyway to tell if KH is high enough from that?